Letter to Congress: U.S. production of Mo-99 for medical radioisotopes

Production of the world's most important radiopharmaceutical, Tc-99m (the daughter produce of Mo-99), is currently at risk. Used in about two-thirds of all diagnostic medical isotope procedures in the United States, over 95% of the world's Tc-99m is produced at just four nuclear research reactors, all of which are over 40 years old. The oldest, Canada's National Research Universal (NRU) reactor, was recently shut down for repairs after a heavy water leak was discovered on May 15. The source of about 40% of the world's Mo-99, it is not clear if and when the NRU could be restarted, or how to replace its production capacity.[1]

Besides posing a threat to patients' health — the medical alternatives to Tc-99m are less effective, more dangerous, as well as more expensive — the current method used by the world's main Tc-99m producers increases the risks of nuclear terrorism, as it employs weapons-grade uranium. The world needs new Tc-99m production capacities as soon as possible, but it is critical that these new capabilities do not increase the risks of terrorism. The letter, sent on June 15, 2009 to the U.S. House Appropriations Committee and U.S. Senate Appropriations Committee, urges the U.S. Congress to support the construction in the United States of Tc-99m production facilities that employ low-enriched uranium (LEU), which cannot be used for weapons. There are currently two U.S. facilities interested in developing such capacities: the University of Missouri, which would employ LEU targets in a traditional research reactor, and the U.S. nuclear company Babcock and Wilcox, which would employ a new technology to create isotopes in a solution reactor (a technology that uses aqueous LEU fuel and no targets). A new production facility that recently opened in Australia, the OPAL reactor, employs LEU, while plans call for the new European reactor in the Netherlands, PALLAS, to use LEU as well.

At this time of crisis, with many hospitals rationing diagnostic tests, it is critical that the world come together to share the limited supply of available Tc-99m for the neediest patients. It is also time to build a more sustainable supply for the future, without adding to current dangers. Political pressure to start up Canada's MAPLE reactors, which were completed in 2000 but never commissioned, is problematic both because operating the reactors is a safety concern, and because of the negative precedent it would set to ignore Canada's nuclear regulator and good nuclear practice (already, in December 2007, Canada's parliament ordered the restart of the NRU reactor, overruling a Canadian Nuclear Safety Commission order to stop operations because of a license violation).[2] More recently, Steve West, the president of Canadian isotope producer MDS Nordion, has called on the Canadian government to let in a team of international experts to see if they can finish the job and start up the MAPLE reactors.[3] The MAPLEs, constructed as a replacement for NRU, did not perform as designed (when operated as a test at 8MW in June 2003, they were discovered to have a positive power coefficient of reactivity when a negative coefficient was expected); despite attempts throughout 2005-8 to identify the cause of this behavior (involving U.S. national laboratories and the Argentine reactor designer INVAP), a cause was never determined. Thus, in May 2008, Atomic Energy of Canada, Ltd. (AECL) made the decision to end the MAPLE project. A study by the U.S. National Academy of Sciences suggested that the reactor cores of the MAPLEs could be removed and replaced - a cheaper and more certain solution than attempting to fix the current design.[4] Operating the MAPLEs as currently configured, without a thorough understanding of their operating parameters, may be expedient in the short term but sets a very poor precedent for nuclear regulators worldwide, and indeed could be dangerous for Canada itself (for instance, if in a catastrophic event, such as an earthquake, all safety features fail). Instead, the United States and the world need new Tc-99m production facilities that will continue to work safely in the long term, without the use of weapons-grade uranium.

Notes

[1] David Akin, "Leaking reactor may be 'gone for good'; Health crisis feared as Ont. facility shutdown could spark shortage of medical isotopes," Edmonton Journal, May 21, 2009, www.edmontonjournal.com/Technology/Leaking+reactor+gone+good/1615106/story.html.
[2] "Nuclear safety watchdog head fired for 'lack of leadership': minister," CBC News, January 16, 2008, http://www.cbc.ca/canada/story/2008/01/16/keen-firing.html,
[3] "Rod removal begins at Chalk River," CBC news, June 2, 2009, www.cbc.ca/health/story/2009/06/02/medical-isotopes-maple-mds.html,
[4] Committee on Medical Isotope Production Without Highly Enriched Uranium, National Research Council, Medical Isotope Production Without Highly Enriched Uranium, National Academies Press, January 2009 (www.nap.edu/catalog.php?record_id=12569), p. 119.